The present invention relates generally to core samplers and more particularly to a device for collecting vertical core samples of viscous sludge.
Viscous sludges include the semi-solid materials found at the bottom of nuclear waste, chemical, and petrochemical storage tanks, as well as the mud-like sediments found at the bottom of oceans, rivers, deep wells, etc. Wherever viscous sludge is found, it may be desirable or necessary to obtain a representative vertical core sample of it, with the sample retaining strata detail.
Existing sludge samplers, with the possible exception of the Piggot ocean-bottom sampler, may be classified as low velocity samplers in which a pipe or tube is pushed relatively slowly into the sludge, perhaps with some rotation. The push may come by hand, by repeatedly pounding the pipe with an appropriate driving mechanism, or by an expensive, complicated rotary core drilling machine or other apparatus designed for that purpose. Low velocity samplers, in the case of a highly viscous sludge, will have their sample tube plug up after penetrating a depth equal to a relatively low number of tube diameters, preventing the entrance of any additional material. Also, to the extent that the sludge is flowable, low velocity samplers will cause vertical mixing. For harder sludges, existing samplers cannot be pushed into the material because the required force will exceed the buckling resistance of the tubing.
The Piggot ocean-bottom sampler (Bulletin of the Geological Society of America, Vol. 47, May 31, 1936, pp. 675-684, 3 PLS., 1 FIG., Piggot, C. S., "Apparatus to Secure Core Samples From the Ocean-Bottom") appears to have a slowly descending brass sample tube and a surrounding steel bit tube at least contacting, and more likely partially penetrating, the ocean bottom at which time a self-contained, bottom-sensing inertia firing mechanism discharges a powder charge which drives the brass sample tube, steel bit tube, firing mechanism, and other components further into the mud to obtain a core sample. Because the sample tube does not maintain a high velocity throughout the sample collection, but starts by partially penetrating or contacting the mud at very low or zero velocity which then increases with the powder discharge, some vertical mixing of the sludge will occur, at least in the top portion of the sample. The ocean-bottom sampler appears unsuited for use in sampling the sludge of radioactive waste tanks because most of its reusable components, along with the sample tube, are driven into the contaminated sludge.